Engine starter gearing



ec. 28, 1948. R. e. DICKENS 2,457,213

' ENGINE STARTER GEARING Filed July 31, 1946 2k .32 39 ,1? I 2% i 2 1 um 3? mm 12 w 16 4 6 z Patented Dec. 28, 1948 ENGINE STARTER GEARING Richard"G. Dickens; Elmira Heights, N. Y., as sign'or tit-Bendix Aviation Gorporation,a cor poration of -Delaware Application July31, 1946, SerialNo. 687;246

(Cl; M -7') 3 Claims. b I The-present invention'relates toe-rigine starte'r gearing and'more particularly to a form of-dr-i-ve which is especially adapted ior use-where a small internal combustion engine is used to start a large engine;-

'In engine starters oi the type which-autmati- (sally-engage the drive when the sourceof power is energized', there is a peak torque developed" when the drive is first established which imposes excessive sti-esses on the partsif some form of yielding driving connection is not'utilize'd-r In the: smaller types of drive-this yielding driving connectionisusu'ally in the formof an-elastic element such as a spring, while in the larger 'or heavy duty types: it is customary-to utilize a-preset friction clutch to limit by slippage-the maximum torque transmitted;-

Transmissions of this kind are well adapted fortheir purpose when an electric star-ting motor is used as a source of power, since the torque-developed by such a motopincreaseswith reductionof-the'rotative speed, and reaches a maximum when the motor is stalled. They are not soap propriate for connecting a small internal com bustion engine to start a large engine however, since the torque ofthe small engine diminishes with reduction of speed below a fairly high value, and becomes zero when the engine stalls. For starting installations of the latter type therefore, it is desirable to have a -drive which will transmit substantially. no torque when the starting engine is idling so as'to avoid" stalling the starting engine, but which will build up to a maximum torque at or about the speed at which the starting engine is adapted to deliver its'-maximum torque.

It is an object of thepresent invention-taproprovide a novel engine starter drive" of" the automatically engaging and disengaging type which incorporates a yielding connection of variable torque capacity.

It is another object to provide such a device in which the torque capacity of the drive varies substantially in accordance with the speed of the prime mover becoming negligible when the prime mover is idling.

It is another object to provide such a device which incorporates means for automatically disengaging the drive when the main engine starts.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and an enlarged 'coun-terbore "l receiving 'a bushing w servin as a bearing for one end oiascreiifishait 9; the opposite" end of which 'isiournall'ed in a suitable 'fixed bearing I l A pinion I 2' i's" thread ed on "the screw shaft 9 for longitudinal move i ment into and out =of' mesh 'with'a' gear l-(rvi fh'il'i? is connected in any suitabIe man ne'r to the ci-ank sha-ft'ofthe main engine to be startedi The 'pin ion I2 is n'orinally mai'nliainefi iliibSidlISOSiiifdlf'" against aback stop- M by: means of-air anti spring! 5, and the'bperative position of'th'pimoii is defined-by "a'=stop hilt I 5 suitably med as-undiscated-on the end of the screwshaft 9? i Centrifugal clutch means-' for connect-i'rr tlie drivingclutch member 4"tstnescrew snaf 9 1s providedcoinprising' a driven-clutch splin'ed on the end 0f the *scrwshaft' 9-" cated at lfl -"in*positi'on to-surrouiid th-dr vi 7 clutch member 4 and a plurality-"of iieXiblcli-lt-h shoes l8 connected" to r6tate' with the drainer clutch-member! with freedo for radialmeve merit into' fri I nar-engasement'with tne intiiieii of thedrum- 1; l a

As best shown in Fig. 2 each clutch shoe comprises a flexible band l9 rigidly attached at one end as indicated at 2| to a bifurcated block 22 which is mounted for radial sliding movement on a vane 23 extending radially from the driving clutch member 4. The block 22 and vane 23 are provided with registering slots 24 and 25 respectively adapted to receive a rectangular key 26 traversing the slots and provided with terminal shoulders 21, 28 engaging the exterior of the block 22. A spring 29 seated in a recess 3| in the vane 23 bears on the key 26 and thereby normally presses the block 22 inwardly so as to hold the clutch shoe l8 out of engagement with the drum IT.

The band 19 of the clutch shoe I8 is provided exteriorly with a suitable friction lining 32, and

the open end of the clutch drum I! in position to bear against the side of the driving clutch member 4 and is retained therein by a lock rin 39 so as to enclose the clutch and limit relative longitudinal movement of the clutch members.

A mesh enforcing spring 4| seated in a counterbore 42 in the end of the screw shaft and hearing against the end of the power shaft 2 urges the screw shaft to the right in Fig. 1, such movement being limited by the engagement of a shoulder 43 on the backstop key M with the interior of the clutch drum H. In order to facilitate assembly and disassembly of the parts, the backstop member I4 is attached to the screw shaft 9,by means of a screw-'44 access to which is permitted by a radial opening 45 through the hub of the clutch drum ll.

' In operation, starting with the parts in the positions illustrated, rotation of the power shaft l at idling speed by the starting engine causes rotation of the driving clutch member 4 and clutch shoes I8, but such rotation is not transmitted to the driven clutch drum l1 since the clutch shoes are held out of engagement therewith by the springs 29. When it is desired to crank the main engine, the starting engine is accelerated to its efficient operating speed, whereby the clutch shoes l8 are moved out by centrifugal force into contact with the interior of the clutch drum ll, such movement being permitted by the sliding connection of the blocks 22 on the vanes 23 of the driving clutch member 4, and by the flexibility of the elements of the clutch shoes. The consequent rotation of the driven clutch drum I! is transmitted to the screw shaft 9 thereby causing traversal of the pinion [2 into mesh with'the engine gear l3 until it engages the stop nut l6 whereupon the rotation of the pinion I2 is transmitted to the engine gear.

The consequent application of load to the starting engine tends initially to slow it down, but this reduction in speed causes the pressure of the clutch shoes I8 against the drum I! to be relieved progressively so as to prevent stalling the starting engine and to enable it to operate at its maximum efliciency. The main engine is thereby, gradually brought up to cranking speed without the application of excessive stresses to 4 the parts of the drive, and in such a manner as to most efiiciently utilize the characteristics of the starting engine.

When the main engine starts, the acceleratio of the engine gear l3 returns the pinion l2 to idle position thus disconnecting the starter drive, whereupon the starting engine may be allowed to idle, or may be de-energized if a repetition of the starting cycle is unnecessary. I

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and various changes may be made in the arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In a transmission for connecting a small internal combustion engine to start a large internal combustion engine, a power shaft rotated by the starting engine, a driving clutch member fixed thereon, a screw shaft slidably journalled in the driving clutch member, a pinion threaded on the screw shaft for movement into and out of mesh with a gear of the engine to be started, a driven clutch drum surrounding the driving clutch member and non-rotatably connected to the screw shaft, a centrifugal clutch means mounted on the driving clutch member to rotate therewith with freedom for radial movement into engagement with the driven clutch drum and yielding means for normally holding the centrifugal clutch member out of engagement with the clutch drum.

2. A transmission as set forth in claim 1 in which said centrifugal clutch member comprises a flexible band attached at one end to the driving clutch member.

3. A transmission as set forth in claim 1 in which said centrifugal clutch means comprises a flexible band attached at one end to the driving clutch member, said band having a friction lining adapted to engage the interior of the clutch drum, and a flexible weight member attached to the band.

RICHARD G. DICKENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date ,354,157 Bendix .a Sept. 28, 1920 1,983,661 Frantz Dec. 11, 1934 1,994,141 Madden Mar. 12, 1935 2,203,795 Nardone June 11, 1940 2,255,0 5 Sekella Sept. 2, 1941 

